A covalent bond is also called a molecular bond. it’s the chemical bond that involved the sharing of electron pairs between the atoms.
One way in which classification is used at school is the separation of different subjects and subject materials. For instance one day you may go to a math class, while another day you may go to a french class.
I feel like it's four because of the eco left on
MRNA is the answer, hope this helps
Rotifer’s cilia draw a vortex of water into its mouth and the rotifer then sifts the food